Materials Literature
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Infrared-to-visible upconversion obtained under continuous-wave infrared laser excitation has been investigated in Pr 3+ -doped chalcohalide glasses for different halide (Cl, Br, I) modifiers and Pr 3+ concentrations. The excitation wavelength dependence suggests two different upconversion mechanisms. When the excitat…
X-ray-absorption near edge structure (XANES) measurements have been performed to investigate the local electronic structures of the Fe-catalyzed and stabilized carbon nanotubes (CNT) with various diameters. The intensities of the π*- and σ*-band and the interlayer-state features in the C K-edge XANES spectra of these…
Durch Addition von Nitrenen, Carbenen oder Radikalen gelingt die Herstellung löslicher, einsträngiger Kohlenstoff-Nanoröhren (gezeigt ist hier das carbenfunktionalisierte Addukt), deren Charakterisierung – ein zentrales Problem in der Nanoröhrenchemie – einfach und unproblematisch ist.
The lattice location of phosphorus dopant atoms in n-type homoepitaxial diamond {111} films grown by chemical-vapor deposition has been investigated by Rutherford backscattering spectrometry and particle-induced x-ray emission under ion-channeling conditions. It is found that phosphorus dopant atoms occupy the substit…
Individual dendritic branches can solubilise hydrophilic dyes in apolar media. The functional group at the focal point of the dendritic branch plays a key role in the dye uptake process. Supramolecular interactions between carboxylic acid and amine groups have been shown to be effective in enabling efficient solubilis…
An isomeric family of eighteen triisopropylsilyl-capped phenylene ethynylene pentamers (molecular formula C60H62Si2) has been prepared by using fast parallel synthesis, for organic electroluminescence. Each pentamer was grown on a polymer support of propylaminomethylated polystyrene by using a series of palladium-cata…
Oxoanionen der p- und d-Block-Elemente wie SiO44−, PO43−, SO42− und CrO42− sind weit verbreitet. Der vollständige oder teilweise Ersatz der Oxogruppen durch isoelektronische Imidogruppen (NR) führt zu homoleptischen Polyimido-Anionen [E(NR)x]z− bzw. heteroleptischen Imidooxo-Anionen mit der allgemeinen Formel [OyE(NR)…
The structural, optical and mechanical properties of orthorhombic ternary nitride crystals have been analysed theoretically with first-principles calculation. Our results indicate that these nitrides possess fairly large optical bandgap (4-6 eV), second-order nonlinear optical susceptibility (13-18 pm V -1 ), and bulk…
At U <1 V nearly the entire voltage in liquid crystals (LC) and in solutions of dyes in LC is applied to the near-electrode regions. In this range of voltages, the Schottky emission through a dielectric layer is the electric current flow mechanism transport. A thin (several nanometres) dielectric layer is formed throu…
Vier ausgehöhlte PW9O349−-Ionen (siehe Bild, blaue Polyeder) werden in den Heteropolyoxometallaten [(PM2W10O38)4(W3O14)]30− (M=Y, Eu) durch acht MIII-Ionen und sieben W-Atome zusammengehalten, welche zusammen ein [M8W7O30]6+-Gerüst aufbauen (Bildmitte). Im Festkörper besteht eine starke Wechselwirkung zwischen den Ani…
Upon continuous wave excitation around 1 μm, a YVO4 crystal codoped with ytterbium and holmium exhibits intense red emission originating in the F55 level and considerably weaker green emission originating in the S52 level of Ho3+. The ratio of the red to green emission intensities is 17:1 at 300 K. The dependence of t…
Nanoporous silica thin films with low dielectric constants were deposited by gas evaporation of SiO2 nanoparticles in an argon atmosphere. With increasing gas pressure during the evaporation, the dielectric constant decreases, while the porosity increases. The correlation between the dielectric constant and porosity i…
Polydentate bridging ligands can be used to link small polyoxo-alkoxo-metalate units to form supramolecular clusters. In the title compound, twelve μ4-bridging squarato groups connect eight trinuclear methoxo-oxo-vanadate units to form a tetradodecanuclear cubic framework (see picture), in whose cavity six n-butyl gro…
Bent by oxidation! A polyaniline (PAn, blue) coated cantilever acts as an electro-driven microdevice. Reversible oxidation/reduction of the PAn results in reversible deflection of the cantilever (see picture) originating from the electrostatic repulsion of the charged polymer chains of PAn2+ (green).
Ultrasound radiation can be used to synthesize a variety of mesporous materials. The reaction time is considerably shorter than the conventional methods. Ultrasonic waves can be further used for the insertion of amorphous nanosized catalysts into the mesopores. A detailed study demonstrates that the nanoparticles are…
Oxo anions of p- and d-block elements, for example, SiO(4)(4-), PO(4)(3-), SO(4)(2-), and CrO(4)(2-), are commonly encountered species. The full or partial replacement of the oxo ligands by isoelectronic imido (NR) groups generates homoleptic polyimido anions of the type [E(NR)(x)](z-) or heteroleptic imidooxo anions…
Exciton-coupled circular dichroism of the porphyrin Soret band of triblock copolymers prepared from chiral isocyanide monomers and an achiral tetraphenylporphyrin derivative (TPP) provides a novel method for determining the helical sense of poly(aryl isocyanide)s (see the schematic representation of the structure).
We consider the quantum properties of an elastic bar subject to compression. If strain rather than stress is held fixed, the system remains stable beyond the buckling instability, supporting two potential minima. The classical equilibrium transverse displacement is analogous to a Ginsburg-Landau order parameter, with…
Synthesis of highly ordered three-dimensionally interconnected mesoporous hydrocarbon polymer networks exhibiting Bragg X-ray diffraction is reported by replicating the mesoporous MCM-48 and SBA-15 channel frameworks.
Rigid, dendritic poly(paraphenylene)s are excellently suited as sensitive and selective coatings for gravimetric sensors (quartz microbalances), since they incorporate guest molecules reversibly into their interior voids. The variety of their potential designs allows an optimal match of these multitalented hosts to th…